Molecular phylogeny and biogeography of the genus Ilex L. (Aquifoliaceae)

Abstract

The chloroplast atpB-rbcL spacer was sequenced for 115 species of Ilex and for Nemopanthus mucronatus (Aquifoliaceae). In addition, rbcL sequences were obtained for 47 selected species. Taken together with fossil records in the literature, the data indicate that: (1) the lineage Ilex was already cosmopolitan long before the end of the Cretaceous. A relative test of the rate of nucleotide substitution indicates that extant species do not represent the entire lineage because of the extinction of its basal branches. The common ancestor of the extant species probably appeared at the upper Tertiary. (2) Several Asian/North American disjunctions are observed, as well as North American/South American relationships. The directions of these relationships are yet to be determined. The African species Ilex mitis is closely related to Asian species. Ilex anomala (Hawaii and Tahiti) is related to American species. Ilex perado and Ilex canariensis (both in Macaronesia) have totally different relationships, the former being related to Eurasian species, while relationships of the latter remain obscure. (3) Gene trees substantially contradict the systematics of Loesener. Nemopanthus, closely related to Ilex amelanchier, is nested in the genus Ilex. The family Aquifoliaceae is organized in four groups, each of them having a geographic or ecological peculiarity.